First, internal energy (U) is the sum of all forms of microscopic energy in a system. It includes all the kinetic energy (the motions, rotations, and vibrations) of tiny particles and all the potential energy of those particles interacting with each other. Think of Pandora’s box (in the original myth, it’s a jar, not a box!) rollicking with buzzing, sparking, invisible particles of evil and mischief inside.…
